With just weeks to go before US President Donald Trump and North Korean leader Kim Jong-un are expected to hold their first summit, Pyongyang on Sunday criticised Washington for its continuing "pressure and military threats" as the two countries prepare for a historic summit.

The North's official news agency quoted a foreign ministry spokesman warning the US about its position that such pressure will not be eased until North Korea gives up its nuclear weapons completely.

Mr Trump and senior US officials have suggested repeatedly that Washington's tough policy toward North Korea, along with pressure on its main trading partner China, have played a decisive role in turning around what had been an extremely tense situation.

The spokesperson warned the claims are a "dangerous attempt" to ruin a budding detente on the Korean Peninsula after Mr Kim's summit late last month with South Korean President Moon Jae-in.

At the meeting, Mr Kim agreed to a number of measures aimed at improving ties between the North and the South, and indicated he is willing to discuss the denuclearisation of the peninsula, though exactly what that would entail and what conditions the North might require have not yet been explained.

Just last year, as Mr Kim was launching long-range missiles at a record pace, it would have seemed unthinkable for the topic of denuclearisation to be on the table.

But the North's statement on Sunday seemed to be aimed at strengthening Mr Kim's position going into his meeting with Mr Trump. Pyongyang claims Mr Kim himself is the driver of the current situation.

"The US is deliberately provoking the DPRK at the time when the situation on the Korean Peninsula is moving toward peace and reconciliation", the spokesman was quoted as saying. DPRK is short for the Democratic People's Republic of Korea, the North's formal name.

Mr Kim and Mr Trump are expected to meet later this month or in early June.

Mr Trump has indicated the date and place have been chosen and said he believes the Demilitarised Zone that divides the Koreas might be a good venue. Singapore was also believed to be a potential site.

Experts are split over whether Mr Kim's statement made with Mr Moon at the demilitarised zone marks a unique opening for progress or a rehash of Pyongyang's longstanding demand for security guarantees.

Sunday's comments were among the very few the North has made since Mr Trump agreed in March to the meeting.

The spokesman warned the US not to interpret Pyongyang's willingness to talk as a sign of weakness.

He did not explicitly mention the Kim-Trump summit, and Pyongyang has yet to make any formal announcement of their planned meeting.

Tensions have run high between the two men over the last year, with both leaders trading threats of war and colourful personal insults that sparked global concern.

Before Mr Trump meets Mr Kim, Washington is hoping to gain the release of three Korean-Americans accused of anti-state activities. Mr Trump hinted the release of Kim Dong Chul, Kim Hak Song and Tony Kim was in the offing.

There was no sign of an imminent release on Sunday, though the men had reportedly been moved to the capital.

The White House, meanwhile, has announced a separate meeting between Mr Trump and Mr Moon at the White House on May 22 to "continue their close co-ordination on developments regarding the Korean Peninsula".